(a) Field of the Invention
This invention relates to a novel adhesive composition which contains an aqueous emulsion as its principal component and is suitable for ceramic tiles.
(b) Description of the Prior Art
Adhesive compositions for ceramic tiles (hereinafter called "emulsion adhesives") containing an aqueous emulsion have conventionally been required to emulsify a resinous tackifier, one of their components, with a surfactant so as to mix the resinous tackifier in the aqueous emulsion, or to render a part of the resinous tackifier soluble in water or to subject the resinous tackifier to some treatment such as carboxylation so as to permit easy mixing of the resinous tackifier with the aqueous emulsion.
Such emulsion adhesives are of the single-pack type and can thus be used immediately after removal from the can. They can be used to apply ceramic tiles readily not only on such bases as mortar but also on smooth surfaces such as on new types of building materials such as plywood, gypsum wallboard and slate which are base materials difficult to apply ceramic tiles thereon by the conventional adhesion method relying upon cement and have thus not been used as bases for ceramic tiles. These adhesives are also free from pollution because they are aqueous emulsions. Therefore, emulsion adhesives have been used extensively in applying indoor tiles. However, adhesives of this sort have poor waterproofness compared with conventional cement-base adhesives and have resulted in separation of indoor ceramic tiles where water is often splashed, such as in bathrooms, to say nothing of outdoor ceramic tiles. In addition, these emulsion adhesives are not fully effective until water, which is contained in the adhesives, sufficiently evaporates or penetrates into bases so as to dry the adhesives. With mortar as a base, it has been impossible to apply tiles thereon when the mortar has not sufficiently aged or fully dried. Further, it has been impossible to use the above emulsion adhesives for such tiles which do not absorb water at all as porcelain tiles or cold-proof tiles.
In response to the recent move toward higher-grade construction, a variety of tiles are often used for both indoor and outdoor applications. To reduce labor and simplify applications, greater use of the above emulsion adhesives is desirable. There has thus been an urgent need for an improvement in the waterproofness of emulsion adhesives in order to permit their use in bathrooms and showerrooms and in their increased applicability to insufficiently-aged fresh mortar bases and to non-hygroscopic tiles such as porcelain tiles and cold-proof tiles in order to prevent tile cracking and breakage due to frost in cold climates.